I had a slight leak at the rear main last spring. It was just enough to leave a drop on the garage floor if the truck sat for a couple of days. Switching to Mobil high mileage oil seems to have stopped the leak.
It may be the pan arches, you may want to take a mirror to the rear one and see for sure. As for the front one remove the stone guard and take a real good look at the seal and arch and see which is leaking. later robbie